Messages in this thread | | | Date | Fri, 29 Apr 2016 16:29:13 +0200 | Subject | Re: [RFC v5 4/4] gpio: dt-bindings: add gpio-mmio bindings | From | Linus Walleij <> |
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On Fri, Apr 29, 2016 at 2:53 AM, Christian Lamparter <chunkeey@googlemail.com> wrote:
> From: Álvaro Fernández Rojas <noltari@gmail.com> > > This patch adds the device tree bindings for the gpio-mmio. > The gpio-mmio is already part of a the GPIO generic library. > > Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com> > Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
I share your ambition to create something generic for this class of hardware(s).
> +Bindings for the generic driver for memory-mapped GPIO controllers. > + > +Required properties: > + - compatible: should be "linux,gpio-mmio"
Why? "memory-mapped-gpio" sits nicely with me.
Read another very generic binding for inspiration: Documentation/devicetree/bindings/leds/register-bit-led.txt
> + - reg-names: must contain > + "dat" - data register > + may contain > + "set" - data set register > + "clr" - data clear register > + "dirout" - direction output register > + "dirin" - direction input register
I would just be more verbose:
data-in-register data-out-set-register data-out-clear-register direction-output-register direction-input-register
Some should be optional so we can support input-only and output-only GPIO controllers too.
I would take this opportunity to add bindings also for stuff that the generic MMIO driver does not support today but could be made to support:
open-drain-register open-source-register debounce-register
etc
> +Optional properties: > + - ngpio: specifies the number of gpio mapped in the register.
Just reference the generic docs.
> + - big-endian: force big endian register accesses. > + - big-endian-byte-order: assign GPIOs in reverse order. > + - unreadable-reg-set: data set register is not readable. > + - read-output-reg-set: cache value set for reads. > + - unreadable-reg-dir: dirout/dirin register is not readable. > + - no-output: GPIOs are read-only.
I think it's better to imply that if there is no data-in-register specified, then it is output-only etc.
> +The GPIO generic library provides support for memory-mapped GPIO > +controllers. The configuration is detected by which resources are present. > +The simplest form of a GPIO controller that the driver support is just a > +single "dat" register, where GPIO state can be read and/or written. > +However, the driver supports far more: > + - 8/16/32/64 bits registers. The number of GPIOs is automatically > + determined by the width of the registers. > + - GPIO controllers with clear/set registers. > + - GPIO controllers with a single "dat" register. > + - Big endian bits/GPIOs ordering.
Skip this. It is Linux-specific.
Yours, Linus Walleij
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